The differentiation of pulpal cells into ondotoblasts during pulpal healing will be studied in two model systems with a view to developing a biological method of pulp capping; i.e. in vitro models using enzymatically separated bovine pulp cells grown in monolayer initially and subsequently in a three dimensional cell culture system. Cells from various concentric regions of the bovine pulp will be stimulated to differentiate into preodontoblasts of odontoblasts and possibly form predentine and dentine. Stimulation will be by biological "materials" such as dentine, predentine, enamel, reduced enamel epithelium, and root sheath. Cells will be cultured against several inert surface variables: Millipore filter (0.45 um and 0.1 um, both sides of the filter), cellophane, Teflon, isobutyl cyanoacrylate, and paper. The surfaces will be modified as appropriate. The commonly used endodontic materials, suitably modified for in vitro experiments will also be investigated. Enzyme biochemistry and histochemistry as well as transmission electron microscope techniques will be used to follow the interactions and differentiation of the cells involved.